Print hammer and actuator construction for high speed printers

ABSTRACT

A PRINT HAMMER ACTUATOR ASSEMBLY FOR HIGH SPEED PRINTERS. TWO ELECTROMAGNETICALLY ENERGIZED ACTUATOR CONSTRUCTIONS ARE PROVIDED, WHICH ARE MECHANICALLY EQUIVALENT BUT OF COMPLEMENTARY GEOMETRY SO THAT THEY CAN BE LOCATED TOGETHER IN A MANNER FACILITATING INDIVIDUAL REMOVAL OF THE ACTUATORS. THE ACTUATORS ARE LOCATED IN DIREACTIONS PARALLEL TO THE LINE OF PRINT BY ALIGNMENT COMBS FASTENED TO A BASE PLATE, AND LOCATED IN DIRECTIONS NORMAL TO THE LINE OF PRINT BY STOP BARS FASTENED TO THE BASE PLATE.

Sept? 20, 1971 J. KONKEL L 3,605,511

PRINT HAMMER AND ACTUATOR CONSTRUCTION FOR HIGH SPEED PRINTERS Filed Ra8, 1969 2 Sheets-Sheet 1 INVENTORS F JOSEPH KONKEL FRANK H. SCHALLERATTORNEYS Sept. 20, 1971 J. QNK EIAL PRINT HAMMER AND ACTUATORCONSTRUCTION FOR HIGH SPEED PRINTERS Filed May 8, 1969 2 Sheets-Sheet 2v Qk lNVfA/TORS JOSEPH KONKEL FRANK H. SCHALLER BY ZMW ATTORNEYS UnitedStates Patent ()ifice 3,605,611 Patented Sept. 20, 1971 3,605,611 PRINTHAMMER AND ACTUATOR CONSTRUC- TION FOR HIGH SPEED PRINTERS Joseph Konkeland Frank H. Schaller, Lynnfield, Mass., assignors to Data PrinterCorp., Boston, Mass. Filed May 8, 1969, Ser. No. 822,985 Int. Cl. B41j9/02; H01f 7/14 US. Cl. 101-93C 14 Claims ABSTRACT OF THE DISCLOSURE Ourinvention relates to high speed printers, and particularly to a novelhammer actuator construction.

High speed printers of the line at a time type have long been known inthe art, and have reached a high state of development. Such printers arecommonly used at line rates of 200 to 1200 per minute. Since the usualcharacter spacing required is on the order of per inch, print hammeractuating mechanisms of considerable complexity have evolved in aneffort to make maximum utilization of the space surrounding the printhammers, while dissipating the relatively large amount of energyrequired for printing. In general, electromagnetic actuators have beenused, in which a pulse of current is applied to a coil to attract anarmature and move the print hammer, either directly or through anintermediate hammer actuator, to cause the hammer to strike against thepaper, ribbon and type carrier. In order to make the necessary amount ofmechanical energy available in an actuator of this kind, it has been thepractice to incorporate the electromagnetic drive structure for a numberof columns in a composite module. Commonly, modules of either four orsix hammers or hammer actuators have been employed. Such modules usuallyinclude a combination of geometrically complementary actuators, onehaving an actuating arm extending directly away from the armature, andanother having an actuating arm at 90 to the armature, together with acombination core construction in which several electromagnetic elementsare interlocked in a single block. The resultant structure is relativelyefi'icient, and thousands of printers incorporating such modules havebeen made and used. However, not only is the manufacture and assembly ofeach module a complex procedure, but the completed modules requireindividual positioning relative to the line of print, and adjustment andmaintenance are difficult and time consuming. The objects of ourinvention are to simplify the construction of high speed printers and tofacilitate their manufacture, adjustment and maintenance.

The above and other objects of our invention are obtained by a novelprint hammer actuator construction wherein each print hammer actuator isindependent of the others but in which means are provided for aligningthem in groups when they are installed, whereby an individual actuatorcan be removed for replacement or service, but in which large numbers ofactuators are aligned at the same time.

Briefly, a print hammer actuator assembly constructed in accordance withour invention comprises, on either side of the line of print, and belowa bank of print hammers, an outer bank of hammer actuators eachcomprising an electromagnetic core with an armature pivotally attachedthereto and carrying an actuator arm that extends inward towards theline of print into engagement with one of the bank of hammers arrangedbelow the line of print. The hammers are suspended by a pair of leafsprings from a support bar that extends over the actuator assembly.Within each outer bank of actuators is an inner bank of actuators, oneither side of the line of print, comprising an electromagnetic coreassembly that is the same shape as the core assemblies of the outer bankexcept that it is rotated by Each actuator of the inner bank furthercomprises an armature connected to an actuator arm at 90, which actuatorarm engages a hammer displaced by two columns from the hammer associatedwith the adjacent actuators of the outer bank. A pair of alignment combsare disposed on either side of the line of print, each notched toreceived alternate actuating arms of the inner and outer banks of thatside, and maintain the actuator arms in columnar alignment with thehammers with which they are associated. Inside each alignment comb, andspaced on either side of the line of print, are a bank of independentlyadjustable bottom stops engaging each actuator arm. For each of theouter and inner banks of actuators, there is provided a transversealignment comb that when mounted to the actuator base plate 10- catesall of the actuators of the bank in directions parallel to the line ofprint. Also, for each bank of actuators there is a single stop platethat aligns all the actuators of that bank in a direction normal to theline of print. The result is a construction in which the alignment ofall of the actuators is established before any actuator is installed.Any actuator of an outer bank can be removed without affecting thealignment of the others, and, surprisingly, any actuator of an innerbank can also be so removed, by withdrawing it obliquely upwardly towardthe line of print.

Our invention will best be understood in the light of the followingdetailed description, together with the accompanying drawings, of apreferred embodiment thereof.

In the drawings:

FIG. 1 is a schematic plan view, with parts shown in cross-section andparts broken away, of a print hammer and actuator assembly in accordancewith our invention;

FIG. 2 is a schematic cross-sectional view, taken essentially along thelines 22 in FIG. 1;

FIG. 3 is an elevational view of a detail of FIG. 2, taken substantiallyalong the lines 33 in FIG. 2, with the actuator arm omitted;

FIG. 4 is a schematic perspective sketch of one of the actuator arms andarmatures of the apparatus in FIGS. 1 and 2;

FIG. 5 is a schematic perspective sketch of a portion of the alignmentcomb and stop assembly forming a part of the apparatus of FIGS. 1 and 2.

Referring now to FIGS. 1 and 2, the apparatus of our invention comprisesan actuator base plate 1, formed at the sides with a pair of elongatedapertures 2 and with a central aperture 3. As shown in FIG. 2, the baseplate 1 is secured to a relatively massive cast iron base frame 4 by asuitable conventional means, such as the bolts 5 and 6. Preferably, theactuator base plate 1 is located on the frame 4 by dowels in the frame,with the bolts such as 5 and 6 passing through clearance holes so thatthey serve to secure the actuator base plate to the frame, but do notinterfere with the location of the frame relative to the plate by meansof the dowels.

A pair of brackets 7 and 8 are secured to the plate 1 at either end, asshown in FIG. 1, and support a transverse bar 9, shown fragmentarily inFIG. 1 and in crosssection in FIG. 2, that serves as the main supportfor the print hammers. The print hammers are preferably of the formshown in FIG. 2, and are each supported by a pair of leaf springs 11 and12. The springs 11 and 12 are in turn secured to a channel 13.

The channel 13 is located on the beam 9 by suitable means, such as adowel, not shown, and a shoulder screw 14, that serves as a removabledowel. Conventional fasteners, such as bolts, not shown, serve to securethe channel to the beam.

As best shown in FIG. 1, the hammer support springs, such as the uppersprings 11, are arranged in complementary pairs such as 11a and 11b sothat each pair can be secured by a single bolt 15. The lower springs 12are similarly arranged to be secured in pairs by bolts 16.

The hammers are each arranged to be actuated by a different one of a setof actuators. The actuators are divided into an inner group, comprisingactuators such as that shown at 17 in FIG. '2, and an outer group,comprising actuators such as that shown at 18 in FIG. 2.

As will appear, the actuators 17 and 18 are mechanically equivalent, butare of complementary form to enable them to be assembled in closelyadjacent relationship. Each actuator comprises a core, anelectromagnetic coil wound on the core, an armature, and an actuator armconnected to the armature and pivoted to the core.

Specifically, each actuator 17 comprises a core member 19 formed with aslot as indicated at 20 to provide a core arm 21 on which is wound anelectromagnetic coil 22. As shown, the core 19 is secured to theactuator base plate 1 by means of a bolt such as 23 so that part of thecoil 22 extends down through the aperture 2 in the plate 1. A pair ofcars 24 are formed on the core 19 to anchor a pivot pin 25 that servesto mount an actuator arm 27, for the actuators 17, or a correspondingactuator arm 28 for the actuators 1 8.

The actuator arms such as 27 are connected to an armature 29 thatextends at right angles to the actuator arm 27. The actuator arms 28 areconnected to geometrically similar armatures 30 that are in alignmentwith the arms 28.

As best shown in FIGS. 3 and 4, the pivot pins 25 cooperate withsuitable bearings 31 mounted in the actuator arms such as 28. Similarbearings are provided in the arms 27.

The outer actuators 18 are secured to the base plate 1 by means of boltssuch as 32 extending parallel to the core arms 20. It will be apparentthat the cores 19 and 19a of the separate forms 17 and 18 are identical,except that one is rotated 90 with respect to the other, and thecorresponding threaded mounting hole similarly displaced. The mountingbolts 23 and 32 extend through clearance holes in the base plate 1 sothat they do not serve to locate the actuators 17 or 18, but merly tohold them down after they have been located. Positioning of theactuators is accomplished by a series of locating combs and stop plates,next to be described.

An important advantage of the actuator construction just described isthat the armatures 29 and 30 extend over a portion of the ears 24. Theears thus form a part of the magnetic circuit. To permit that result,the ends of the core legs 20 and 21 are flat and coplanar with thecorresponding ends of the ears 24. And the pivot pins 25 are locatedbelow the common plane of those ends of the core legs and ears.

Referring to FIGS. 1 and 2, four identical actuator alignment combs 33are each provided with a series of recesses such as 34 that serve tolocate the actuators 17 and 18 in directions parallel to the line ofprint. At the rear of each alignment comb, and located above it, is astop bar 35, shown in fragmentary form over the first and third combsfrom left to right in FIG. 1, in full for thesecond comb and omitted forthe fourth comb. The edges of these stop bars 35 locate the actuators 17and 18 in directions normal to the line of print. The bars arepositioned by locating holes 37, as shown at the upper.

right in FIG. 1, and by a lower aperture 38 that is elongated in adirection parallel to the line of print.

In accordance with our invention in its broader aspects, the stop bars35 could be omitted and their function performed by the inner edges ofthe spaces between the teeth of the combs 33. That would compli cate themanufacture of the combs, however, and we prefer the construction shown.

The apertures 37 and 38 are adapted to receive dowel pins secured to thebase plate 1. The dowel pins are precisely located, and the elongationprovided for the lower aperture 38 is to account for minor changes indimension lengthwise of the combs 33 without allowing any movement ofthe combs angularly with respect to the line of print. Similarly, thestop bars 35 are provided with apertures 39, as shown at the upper leftin FIG. 1, and elongated apertures 40 at the other end, to accuratelyposition the stop bars on the dowel pins such as 41. The stop bars 35and combs 38 may be firmly secured to the base frame 4 by means such asthe bolts 42 extending through clearance holes such as 43 in the comb,stop bars, and base plate 1.

[For clarity, FIG. 2 shows only one inner actuator assembly 17 and oneouter actuator assembly 18 located on d'nferent sides of the line ofprint. In practice, an inner set of actuators 17 will be located on theleft side in FIG. 2, and an outer set such as 1-8 will be located on theouter side at the right in FIG. 2. The pivot pins 25 for each of themating units 17 and 18 on a given side of the line of print will be inaxial alignment in a line parallel to the line of print. The exactarrangement is shown in FIG. 1, for the central group of four actuators,showing how they are arranged side by side.

The dimensions of the parts in directions parallel to the line of printis determined by the character spacing in the printer. Thus, if thecharacters are to be printed on onetenth inch centers, the width of onecolumn is one-tenth. of an inch and the thickness of the actuator coreassemblies will be two columns wide, or two-tenths of an inch. The teeth34 of the combs 33 will be two columns wide with two column spacesbetween teeth. Confronting combs are relatively displaced by twocolumns, and corresponding combs on opposite sides of the line of print,such as those locating the outer actuator 18, are displaced by onecolumn. The result is that the actuating arms of the print hammeractuators are interdigitated in the order shown in FIG. 1.

It will be apparent by comparing FIGS. 1 and 2 that the only overlap inthe actuators 17 and 18 is in the coils 22 of the inner actuators 17that extend under the corresponding adjacent actuators 18 withclearance. The arrangement is such that any of the actuators 17 and 18can be removed individually.

The actuator arms 27 for the actuators such as 17 have a slight netclockwise moment, as seen in FIG. 2, by reason of the additional weightof the armature portion 29. In the rest position, each such arm 27 isheld down against a resilient stop pad 47 that is mounted on a stop comb48. As best shown in FIG. 5, the stop comb 38 comprises a flange portion49 arranged to be bolted to a screw plate 50. The screw plate 50 extendslengthwise across the base plate 1 in a direction parallel to the lineof print, as shown in FIG. 1. Referring again to FIG. 5, an upstandingportion 51 of the stop comb is formed with laterally projecting teeth58, on each of which a stop pad 47 is mounted. The pads may be of rubberor the like. Mounted with each of the stop combs 48 is an alignment comb53 provided with upstanding teeth 54 that separate and guide theactuator arms such as 2-7 and 28.

The springs 11 and 12 mounting each hammer 10 hold the associatedactuator arm such as 27 and 28 down against the stop pads 47 until thehammer actuator is energized by application of a pulse of current to itsasso ciated coil 22. When that occurs, the armature such as 29 of theactuator such as 17 is drawn toward the core arm 21, causing theactuator 27 to rise and drive the associated hammer upwardly, to contactwith the paper, transfer sheet and moving type carrier to form animpression.

Flight time adjustment of the hammers 10 is accomplished by adjustmentof the bottom stops 47 on the stop combs 48. For that purpose, screws 57are threadedly secured to the base plate 50 and engage the individualteeth of the stop comb 48 so that individual adjustment for each columncan be provided.

While we have described our invention with respect to the details of apreferred embodiment thereof, many changes and variations will occur tothose skilled in the art upon reading our description, and such canobviously be made without departing from the scope of our invention.

Having thus described our invention, what we claim 1. A hammer actuatorassembly for high speed printers, comprising:

an actuator mounting plate, an alignment comb secured to said plate andhaving a base portion and teeth projecting from said base portion, saidteeth having parallel sides extending along lines normal to apredetermined plane,

a stop bar secured to said mounting plate adjacent said comb and havingan edge normal to said sides, and

a set of actuators,

means for removably securing each actuator to said plate betweenrespective teeth of said comb,

each of said actuators cooperating with a respective hammer,

each actuator having two sides engaging said teeth and held in alignmentthereby, and

a third side engaging said edge of said stop bar to establish lateralalignment of said actuators, said stop bar cooperating with saidsecuring means to prevent lateral movement of said actuators, wherebythe alignment of said actuators is determined by the respectivepositions of said comb and stop bar on said plate.

2. The apparatus of claim 1, in which said actuator each comprise:

a ferromagnetic core on which a coil adapted to be energized by a pulseof current is wound, an actuator arm pivotally mounted on said core, andan armature connected to said arm in position to be attracted to saidcore when coil is energized. 3. The apparatus of claim 2 in which thecores of said actuators on a first side of said recess comprise:

core legs on which said coils are wound about axes normal to said plate,in which the cores of said actuator on the other side of said recesscomprise core legs on which said coils are wound about axes parallel tosaid plate, the coils on said other side partially protruding throughsaid recess.

4. The apparatus of claim 2 in which all of said actuator arms arepivoted about a common axis,

in which the armatures on said first side are aligned with the actuatorarms to which they are connected, and

in which the armatures on said other side extend at right angles to theactuator arms to which they are connected.

5. A hammer actuator for a high speed printer, comprising:

a core piece of ferromagnetic material formed with a core leg on a firstside thereof and an electromagnetic coil wound on said core leg about afirst axis,

a pair of parallel ears extending from said core piece in planesparallel to said first axis,

a pivot pin mounted between said ears and defining a pivot axis normalto said plane,

an actuator arm for cooperating with a print hammer pivotally mounted onsaid pin, and

an armature block of ferromagnetic material connected to said actuatorarm and extending over a portion of said ears and said core leg to beattracted toward said core leg when said coil is energized, said earsforming a part of the magnetic circuit comprising said armature andferromagnetic core piece.

6. The actuator of claim 5 in which said core piece terminates in a flatend,

said ears terminate in flat ends substantially coplanar with said end ofsaid core piece, and

said pivot pin is located below the plane of said ends.

7. The actuator of claim 5 in which said actuator arm extends to anactuating end along a line in alignment with said armature, and furthercomprising:

means forming a threaded mounting recess in said core piece normal tosaid first axis. 9. The actuator of claim '5 in which the maximumdimension of the recited elements other than said coil in directionsparallel to said pivot axis is the width of two columns in the printerin which the actuator is to be installed.

10. The actuator of claim -6 in which said actuator arm extends to anactuating end along a line in alignment with said armature, and furthercomprising:

means forming a threaded mounting recess in said core piece parallel tosaid first axis.

11. The actuator of claim 6 in which said actuator arm extends to anactuating end along a line normal to the extension of said armature, andfurther comprising:

means forming a threaded mounting recess in said core piece normal tosaid first axis.

12. The actuator of claim 6 in which the maximum dimension of therecited elements other than said coil in directions parallel to saidpivot axis is the width of two columns in the printer in which theactuator is to be installed.

13. A print hammer actuator assembly, comprising:

a pair of alignment combs each having projecting teeth two columns wideinterspersed with spaces two columns wide.

means mounting said combs in spaced confronting relation with the teethof one comb projecting toward the spaces between the teeth of the othercomb,

a pair of stop bars each having at least one straight edge,

means mounting each of said stop bars against one of said combs withsaid edge across said teeth,

a set of electromagnetic hammer actuating means, one for each spacebetween comb teeth,

means detachably mounting said actuating means between and engagingdifferent pairs of said teeth of each of said combs and engaging saidedge of one of said stop bars, said actuating means comprising corepieces extending between said teeth end having actuating arms pivotallymounted thereon for rotation about first axes parallel to said edges,and

armatures connected to said arms and adapted to be moved toward and awayfrom said core pieces upon rotation of said arms,

said core pieces, arms and armatures having maximum dimensions indirections parallel to said pivot axes not greater than the width of twocolumns,

the core pieces located between the teeth of one comb projecting towardand into interdigitated relation with the actuators located between theteeth of the other comb and the pivot axes of all of said actuatorsbeing colinear,

said core pieces being formed with core legs,

the core legs of the core pieces engaging one comb being located on theside away from the other comb, and the core legs on the core piecesengaging the other comb being formed on the side of the core piece nextto the comb and extending toward the other comb and beneath saidcolinear pivot axes, and

electromagnetic coils having maximum dimensions not larger thantwocolumns in directions parallel to said axes Wound on all of said corelegs.

14. A hammer actuator assembly for high speed printers, of the line at atime type including a moving type carrier and independent, selectivelyactuable hammer actuators, one for each of a plurality of columns in aline to be printed, comprising:

an actuator mounting plate,

an alignment comb secured to said plate and having a base portion andteeth projecting from said base portion, said teeth having parallelsides forming locating surfaces extending normal to the plane of saidmounting plate,

a stop bar secured to said mounting plate adjacent said comb and havingan edge normal to said surfaces, and

a set of selectively and independently energizable ferromagneticactuator elements, individual detachable means for each actuator elementfor fixedly mounting each actuator element on said plate, each ac- 30tuator element being detachably mounted between diiferent teeth of saidcomb, means for selectively energizing each of said actuator elements,each mounted on said plate between different teeth of said comb,

each actuator element having two sides engaging a corresponding pair ofsaid locating surfaces and held in alignment therebetween, and

a third side engaging said edge of said stop bar to prevent lateralmovement of said actuator elements, whereby said actuator elements areeach independently, selectively actuable and the alignment of each ofsaid actuator elements is independently determined by the relativepositions of said comb, said stop bar and said plate.

References Cited UNITED STATES PATENTS WILLIAM B. PENN, Primary ExaminerE. M. COVEN, Assistant Examiner US. Cl. X.R.

